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V,\o  UNIVERSITY  OF  OREGON  BULLETIN 

Yu>  .5  _ ■ 

Cop,  J NEW  SERIES  JANUARY,  1913  Vol.  X,  No.  5 


CONCRETE  ROADS 


VERSUS 


MACADAM 


e.  h.  McAlister 


Dean  of  the  School  of  Engineering,  University  of  Oregon 


Published  monthly  by  the  University  of  Oregon,  and  entered  at  the  post-oflice  in 
Eugene,  Oregon,  as  second-class  matter 


CONCRETE  ROADS 


VERSUS 

MACADAM 


e.  h.  McAlister 


Dean  of  the  School  of  Engineering,  University  of  Oregon 


I 


CONCRETE  ROADS  VERSUS  MACADAM. 

A NEW  PROBLEM  AT  HAND. 


During1  the  past  decade,  the  improvement  of  public  highways  has 
brought  into  existence  a new  class  of  traffic.  Motor  trucks  and  mechan- 
ical tractors  drawing  trains  of  loaded  wagons  have  in  many  instances 
revolutionized  the  highway  end  of  freight  transportation.  Mechanical 
haulage  is  able  not  only  to  effect  a vast  reduction  in  the  cost  of  trans- 
portation per  ton-mile  on  existing  traffic,  but  also  it  makes  possible  the 
production  of  many  articles  which  hitherto  could  not  be  produced  with- 
out loss,  on  account  of  the  expense  and  delay  in  getting  them  to  market. 

This  is  notably  true  with  reference  to  perishable  products,  but  the 
production  of  such  a staple  article  as  wheat  has  been  subject  to  consid- 
erable limitation.  A few  years  ago,  the  general  freight  agent  of  one  of 
the  great  railroads  of  the  Northwest  stated  that  the  production  of  wheat 
was  limited  practically  to  a belt  12  or  15  miles  wide  on  either  side  of  4 he 
railway  line,  and  that  the  amount  produced  at  greater  distances  did  not 
figure  in  the  sum  total  of  production.  Perhaps  these  limits  have  been 
slightly  widened  at  the  present  time,  but  there  is  no  doubt  that  mechan- 
ical haulage  on  good  roads  could  very  greatly  increase  the  area  of  profit- 
able production  for  both  staple  and  perishable  products,  and  thereby  in- 
crease the  wealth  of  the  state  many  fold,  at  the  same  time  affording  a 
comfortable  living  to  increasing  thousands  on  wide  areas  where  now  a 
bare  existence  would  be  difficult.  Unquestionably  this  is  one  of  the  most 
important  ways  in  which  the  wealth,  population  and  prosperity  of  the 
state  can  be  built  up,  and  it  is  not  surprising  that  the  good  roads  move- 
ment has  attracted  the  earnest  attention  of  all  classes,  both  in  this 
country  and  in  Europe. 

But  mechanical  haulage,  wherever  it  has  become  considerable  in  mag- 
nitude, has  brought  new  problems  and  difficulties.  The  good  macadam 
roads,  which  made  possible  and  brought  forth  the  new  traffic,  have  been 
quickly  destroyed  by  the  traffic — another  case  of  the  offspring  devouring 
its  parent.  The  destruction  of  the  roads  appears  of  course  in  the  in- 
creased cost  of  maintenance  and  repairs.  In  Massachusetts,  during  the 
three  years  preceding  1910,  the  cost  of  upkeep  for  the  state  highways 
rose  from  a little  over  one  cent  to  nearly  6 cents  per  square  yard  per 
annum.  On  many  roads  the  cost  became  so  great  that  water-bound  ma- 
cadam was  abandoned  and  some  other  type  of  surface  was  adopted. 
Other  and  even  worse  cases  will  be  cited  further  on  in  this  Bulletin.  It 
is  true  that  such  serious  conditions  have  not  yet  arrived  in  Oregon,  and 
the  cost  of  upkeep  is  still  comparatively  low.  But  mechanical  haulage 
has  just  begun  in  this  state,  and  it  does  not  require  the  eye  of  a prophet 
to  discern  that  in  a very  few  years  the  same  conditions  will  be  upon  us 
as  are  now  found  elsewhere.  During  the  first  nine  months  of  1912,  the 
number  of  registered  motor  vehicles  in  Oregon  showed  an  increase  of  55 
per  cent  over  the  total  number  registered  in  1911.  A little  foresight  may 
save  considerable  money  to  the  taxpayers  of  Oregon,  and  give  them 
much  better  roads  in  the  meantime. 

[3  j 


SUITABLE  TYPE  OF  ROAD  SURFACE. 


Relative  to  the  matters  mentioned  in  the  preceding  paragraphs,  the 
writer  has  recently  perused  several  thousand  pages  of  road  literature, 
including  the  new  books  on  highway  construction,  the  reports  of  nu- 
merous state  highway  commissions,  the  proceedings  of  recent  road  con- 
gresses and  conventions,  including  the  International  Road  Congress  at 
Brussels  in  1910,  and  the  more  important  articles  in  recent  technical 
periodicals.  The  conclusion  in  all  parts  of  the  world  is  practically  unan- 
imous that  the  standard  water-bound  macadam  is  not  suited  to  the  traf- 
fic of  the  future ; that  mechanical  haulage  has  come  to  stay,  as  an  eco- 
nomical and  social  betterment.  With  scarcely  an  exception,  the  deter- 
mination is  everywhere  expressed  that  the  roads  must  be  made  to  serve. 
Commenting  on  a phase  of  this  subject,  a recent  technical  journal  edi- 
torially remarks : 1 ‘ This  is  not  a matter  of  pleasure  vehicles  and  picnic 

parties.  It  is  an  issue  of  bread  and  butter.  Many  millions  of  dollars 
in  mud  taxes  are  coming  either  out  of  the  people ’s  mouths  or  out  of  their 
pocket  books — depending  upon  whether  they  go  without  adequate  food, 
or  pay  too  much  for  it.  Good  roads  and  mechanical  haulage  will  lift 
this  mud  tax,  will  lower  the  cost  of  living,  and  will  make  community 
existence  possible  under  new  conditions.  Community  existence  will  be 
possible  without  having  people  huddled  together  with  an  ever  increasing 
tendency  of  the  population  toward  the  cities.” 

So  far,  there  is  practical  unanimity,  but  when  it  comes  to  selecting  a 
suitable  type  of  surface  to  replace  the  water-bound  macadam,  there  is 
every  possible  degree  of  divergence  of  opinion.  However,  for  our  present 
purpose,  we  may  roughly  group  the  opinions  under  three  classes : 

First),  there  are  those  who  advocate  the  use  of  some  type  of  pavement 
found  suitable  in  cities,  such  as  standard  asphalt,  bitulithic,  vitrified 
brick,  etc.  These  are  all  admirable  in  most  respects,’  but  their  high  cost 
will  doubtless  prevent  their  adoption  on  country  roads,  except  to  a very 
limited  extent. 

Secondly,  we  may  class  together  the  great  number  of  schemes  which 
are  mere  temporary  palliatives  of  the  difficulty,  such  as  oiling  the  surface 
of  existing  roads,  treatment  with  calcium  chloride  or  various  emulsions, 
or  with  tar.  These  have  their  merits  in  the  way  of  cheapness  and  tem- 
porary relief,  but  do  not  seem  desirable  to  adopt  as  a permanent  policy 
of  road  improvement. 

Thirdly,  there  are  the  advocates  of  a concrete  road,  either  with  or 
without  a bituminous  wearing  surface.  The  first  cost  of  these  roads 
will  generally  be  somewhat  greater  than  for  macadam,  but  they  are  not 
torn  to  shreds  by  motor  traffic,  and  their  cost  of  upkeep  is  low  enough 
to  offset  the  additional  first  cost  in  a comparatively  short  time,  wherever 
the  traffic  is  severe,  as  it  is  likely  to  become  on  our  more  important  roads 
within  a very  few  years.  In  addition  to  their  ultimate  economy,  con- 
crete roads  are  better  than  macadam  all  the  time. 

The  state  Highway  Commission  of  New  York  has  concluded  the  expen- 
diture of  $50,000,000,  voted  a few  years  ago  for  state  roads,  together 
with  some  $15,000,000  raised  by  counties  and  towns.  The  conclusions  of 
the  Commission,  after  spending  $65,000,000  in  constructing  almost  every 
kind  of  road  known,  are  certainly  of  interest,  and  ought  to  carry 
weight  with  thinking  people.  In  a report  issued  in  1912,  discussing  the 


change  of  policy  of  the  Commission  (from  bituminous  macadam  to  con- 
crete), the  following  statement  occurs: 

“Having  these  factors  in  view,  it  seems  wise,  wherever  possible,  ,to 
construct  a foundation  of  concrete  and  to  cover  this  with  a thin  wearing 
course  composed  of  bituminous  material  and  screenings  or  sand,  which 
is  economical  in  first  cost  and  easily  and  cheaply  renewed.  The  foun- 
dation of  a road,  so  constructed,  is  good  for  all  time,  and  the  wearing 
course  serves  the  purpose  of  carrying  all  classes  of  traffic  without  rub- 
bing, raveling,  or  raising  a dust.” 

The  state  of  California  recently  voted  $18,000,000  for  the  construction 
of  trunk  lines,  and  the  Highway  Commission  has  adopted  the  concrete 
base  with  thin  bituminous  surface  for  a number  of  roads  connecting 
towns  on  the  main  line.  Up  to  last  October,  more  than  a hundred  miles 
of  such  roads  had  been  laid  out,  with  78  miles  under  contract.  The 
Highway  Engineer  of  the  California  Commission  is  Mr.  Austin  B. 
Fletcher,  a man  of  national  reputation,  formerly  with  the  Massachusetts 
Highway  Commission  and  special  agent  of  the  United  States  office  of 
Public  Roads.  His  judgment  should  carry  great  weight,  especially  when 
taken  in  connection  with  that  of  the  New  York  commission. 

Between  the  extremes  of  California  and  New  York,  there  is  scarcely 
a state  that  has  not  some  concrete  roads,  and  the  mileage  is  growing 
rapidly. 

Considering  its  many  merits,  and  the  fact  that  in  the  long  run,  it  is 
relatively  inexpensive,  it  seems  probable  that  the  concrete  road,  either 
with  or  without  a bituminous  wearing  surface,  will  become  the  standard 
highway  of  the  future.  It  is  worthy  of  note  that  at  the  last  meeting  of 
the  association  for  standardizing  paving  specifications,  the  committee 
on  macadam  declined  to  present  any  specification  for  water-bound  ma- 
cadam, the  members  of  the  committee  unanimously  agreeing  that  it  is 
not  suited  to  modern  conditions.  Instead  they  presented  specifications 
for  bituminous  macadam,  which  in  Oregon  would  cost  more  than  concrete. 

DECREASING  THE  COST  OF  CONCRETE. 

It  has  been  known  to  scientific  experimenters  for  some  time  that  if 
certain  volcanic  materials  be  reground  with  Portland  cement,  the  result- 
ing blend  can  be  used  to  make  concrete  which  in  point  of  strength  is 
equal  or  superior  to  concrete  made  in  the  usual  manner.  A material 
saving  is  effected  in  cost,  especially  where  cement  is  high  in  price,  and 
a further  advantage  is  gained  in  greater  resistance  to  certain  destructive 
agencies  which  attack  concrete  in  some  locations. 

From  the  known  chemical  composition  of  certain  volcanic  materials 
abundant  in  Oregon,  the  writer  inferred  that  possibly  some  of  them 
might  give  good  results  when  blended  with  cement,  and  accordingly  un- 
dertook a series  of  tests  at  the  civil  engineering  laboratory  of  the  Uni- 
versity of  Oregon.  These  tests  have  been  carried  on  since  last  October 
and  are  still  in  progress.  Already  a few  blends  have  been  found  which 
give  results,  both  in  tension  and  compression,  superior  to  those  obtained 
from  the  same  cement  without  blending.  Some  of  the  results  will  be 
discussed  on  subsequent  pages. 

Blends  of  this  kind,  after  being  prohibited  for  several  years  have  re- 
cently received  the  approval  of  the  German  Government,  following  an 
elaborate  investigation,  and  are  now  permitted  on  Government  work. 

[5] 


M.  Rene  Feret,  Chief  of  the  Laboratory  of  Bridges  and  Roads  of  the 
French  Government,  after  careful  investigation,  reported  in  1908  that 
“The  use  of  puzzolan  in  hydraulic  mortars  in  combination  with  the 
cement  increases  the  strength,  and  in  a great  many  cases  appreciably 
retards  disintegration  by  sea-water.”  Puzzolan  is  a volcanic  material. 

Other  European  authorities  have  reached  similar  conclusions,  includ- 
ing Dr.  W.  Michaelis,  the  great  German  chemist  and  cement  expert,  who 
has  been  called  the  “Dean  of  the  German  cement  industry.” 

It  is  unfortunate  that  some  have  confused  these  puzzolan-Portland 
blends  with  the  so-called  “puzzolan  cements.”  There  is  no  connection, 
other  than  the  mere  accident  of  name. 

The  most  extensive  use  of  cement  blends  in  this  country  has  been  on 
the  250-mile  aqueduct  which  is  in  process  of  construction,  to  furnish 
water  to  the  city  of  Los  Angeles,  California,  and  the  surrounding 
country.  The  amount  of  cement  required  for  this  work  is  about 
1,500,000  barrels,  enough  cement  for  1200  miles  of  concrete  road  15  feet 
wide,  laid  according  to  the  California  specifications.  The  aqueduct  is 
large  enough  to  carry  a fair  sized  stream — equal  to  about  half  the  low 
water  flow  of  the  Willamette  river  at  Eugene.  On  this  work  blends, 
made  by  grinding  together  equal  parts  of  Portland  cement  and  volcanic 
rock,  have  been  used  with  entire  success  during  the  past  four  years. 
The  aqueduct  crosses  the  Mojave  Desert,  and  the  concrete  had  to  be 
laid,  with  a scant  supply  of  water,  in  the  heat  and  drouth  of  the  desert. 
This  furnishes  the  complete  and  final  answer  to  those  skeptics  who  de- 
clared that  concrete  made  with  these  blends  could  not  be  successfully 
laid  in  dry  weather.  A lengthy  account  of  tests  made  and  processes 
used  has  been  given  by  Mr.  J.  B.  Lippincott,  one  of  the  engineers  of 
the  Aqueduct  Commission,  in  a recent  communication  to  the  American 
Society  of  Civil  Engineers. 

Samples,  of  the  blends  above  referred  to  were  sent  to  the  United 
States  Bureau  of  Standards  for  analysis  and  tests.  The  following  is  a 
quotation  from  the  report  of  this  Bureau : 

“You  desired  particularly  to  know  whether  there  was  any  chemical 
reaction  between  the  tufa  and  the  cement.  The  enclosed  report  shows 
that  such  has  undoubtedly  been  the  case.  The  addition  of  tufa  or  puz- 
zolana  to  Portland  cement  undoubtedly  does  not  reduce  the  strength  of 
the  latter  when  in  the  form  of  a mortar  or  concrete.  ’ ’ 

The  engineers  of  the  United  States  Reclamation  service  have  been 
carrying  on  an  extensive  series  of  tests  along  this  line  for  over  five 
years,  using  a great  variety  of  materials  in  making  the  blends.  As  a 
result  of  these  investigations,  cement  reground  with  local  materials  has 
been  adopted  for  the  large  masonry  dams  and  for  the  auxiliary  works 
in  connection  with  a large  earthern  dam,  all  under  construction  by  the 
Reclamation  service. 

Considering  the  very  extensive  tests  referred  to  in  preceding  para- 
graphs, and  the  long  practical  experience  with  blends  in  Europe,  ex- 
tending over  a period  of  more  than  30  years,  and  the  more  recent  ex- 
perience of  over  four  years  on  the  Los  Angeles  aqueduct,  and  in  vieflv 
of  the  still  more  recent  adoption  of  blends  by  the  United  States 
Government  for  the  construction  of  important  dams,  the  only  question 
that  remained  in  the  mind  of  the  writer  was  whether  the  materials 
easily  available  in  Oregon  would  prove  satisfactory  when  reground  with 


Portland  cement.  The  tests  made  at  the  University  of  Oregon  have 
shown  that  one  material  which  is  of  wide  distribution  in  the  Willam- 
ette valley  gives  very  excellent  results,  while  other  materials,  available 
in  certain  localities,  are  also  suitable.  A brief  account  of  these  tests 
will  now  be  given. 

The  proposed  stone  was  first  crushed  to  fragments  not  exceeding  one- 
twentieth  inch  in  diameter.  These  fragments  were  then  mixed  with 
cement  in  definite  proportions  by  weight.  The  mixture  was  then  ground 
to  a fineness  somewhat  exceeding  that  of  the  original  cement  so  that  90 
per  cent  would  pass  through  a No.  200  sieve.  The  finely-ground  mixture 
is  for  convenience  called  a “ blend,”  and  is  subsequently  used  in  the 
same  manner  as  cement.  For  brevity,  the  blends  are  designated  by 
letters,  the  letter  “ A,  ” however,  designating  pure  Portland  cement. 
Among  the  blends  experimented  with,  the  following  may  be  noted: 

“A”- — Pure  Portland  cement. 

“B” — 1 part  cement  to  1 part  “Eugene  puzzolan. ” 

“C” — 2 parts  cement  to  1 part  “Eugene  puzzolan.” 

“D” — 1 part  cement  to  1 part  diatomaceous  earth. 

“E” — 2 parts  cement  to  1 part  diatomaceous  earth. 

“F” — 1 part  cement  to  1 part  “Grants  Pass  puzzolan. 

“H” — 2 parts  cement  to  1 part  slag. 

“K” — 1 part  cement  to  1 part  “Clackamas  puzzolan. ” 

The  stone  designated  above  as  “Eugene  puzzolan’’  was  obtained  at 
Eugene,  but  is  abundant  in  the  Willamette  Valley.  It  is  needless  to  say 
that  the  term  “puzzolan”  does  not  adequately  describe  its  mineralogical 
character;  its  chemical  composition  is  similar  to  that  of  the  tufa  used 
on  the  Los  Angeles  aqueduct.  The  diatomaceous  earth  was  taken  from  a 
deposit  near  Eugene;  it  is  an  excellent  material  for  this  purpose,  but  so 
far  such  deposits  have  been  found  only  in  a few  places  in  Oregon,  and  it 
would  not  therefore  be  generally  available.  The  Grants  Pass  and  Clack- 
amas “puzzolans”  are  similar  to  the  Eugene  puzzolan,  but  not  identical. 
The  slag  in  blend  “ H ” is  a blast  furnace  slag  from  Oswego.  It  is  some- 
times termed  an  artificial  puzzolan,  and  similar  slags  are  often  used  in 
Germany. 

Cement  is  almost  never  used  pure  in  practical  work;  it  is  mixed  with 
sand  or  stone  screenings  to  form  mortar  or  concrete.  Accordingly,  the 
practical  question  with  reference  to  these  blends  is  this:  What  is  the 
relative  strength  of  mortars  made  with  the  blends  and  of  similar  mortars 
made  with  the  same  cement  not  blended?  To  determine  this  question, 
both  tensile  and  compressive  tests  have  been  made.  The  tension 
briquettes  were  composed  of  1 part  cement  or  blend  to  3 parts  sand  by 


[7J 


weight.  Some  of  the  more  important  results  are  shown  on  the  follow- 
ing diagram: 


The  sand  used  was  crushed  quartz,  screened  to  the  same  size  as  stand- 
ard sand.  It  is  of  very  uniform  character,  but  gives  results  in  tension 
that  are  uniformly  about  80  per  cent  of  those  obtained  with  standard 
Ottawa  sand;  accordingly  all  the  tension  curves,  including  curve  “A,” 
have  been  reduced  to  the  basis  of  standard  sand,  to  facilitate  comparison 
by  those  acquainted  with  cement  testing.  The  compression  tests  given 
below  have  not  been  reduced  to  the  basis  of  standard  sand,  because  the 
relationship  is  not  known  for  compression. 

It  will  be  noted  that  all  the  blends  shown  surpassed  the  cement  in 
tensile  strength  at  the  end  of  28  days,  except  blend  “K,M  for  which  the 
28-day  tests  had  not  been  made  at  the  time  the  figure  was  drawn.  The 
tests  made  subsequently  showed  that  blend  “K”  also  surpassed  the 
cement  at  28  days. 

Some  typical  compression  tests  are  as  follows: 

Mortars  similar  in  every  resepect  to  those  used  in  the  tension 
briquettes,  age  2 months : 


lbs.  per  sq.  inch. 

With  cement  3030 

With  blend  “B” 4210 

With  blend  4210 

Mortars  similar  to  tension  briquettes,  except  that  river  sand  was  used 
instead  of  quartz;  age  2 months,  1 week: 

lbs.  per  sq.  inch. 

With  cement 4140 

With  blend  “D” 3010 

With  blend  “E” 5760 


Mortars  composed  of  1 part  cement  or  blend  to  5.22  parts  sand  by 
weight ; the  sand  was  coarser  than  the  above ; age,  2 months : 


[8] 


lbs.  per  sq.  inch. 


With  cement 2526 

With  blend  “B”  2125 

With  blend  “C”  4240 


From  the  results  quoted  above,  and  others  not  here  quoted,  it  has  been 
found  that  blends  composed  of  equal  parts  by  weight  of  cement  and  puz- 
zolanic  material  have  somewhat  less  strength  in  compression  than  the 
original  cement,  but  that  blends  composed  of  2 parts  cement  to  1 part 
puzzolanie  material  by  weight  have  far  greater  compressive  strength 
than  the  original  cement.  However,  it  must  be  noted  that  all  the  puzzo- 
lanic  materials  experimented  with  are  lighter  than  the  cement,  so  that 
equal  parts  by  weight  give  an  excess  of  puzzolanie  material  by  volume, 
and  the  results  obtained  indicate  that  53  per  cent  by  weight  of  cement 
to  47  per  cent  “ Eugene  puzzolan”  will  give  compressive  strength  equal 
to  that  of  the  original  cement  in  either  1:3  or  1:5  mortars;  while  equal 
parts  by  volume  of  cement  and  diatomaceous  earth  will  surpass  the  orig- 
inal cement.  Blend  (<E”  is  practically  equal  parts  by  volume,  the 
diatomaceaus  earth  being  only  about  half  as  heavy  as  cement.  On  the 
Los  Angeles  aqueduct,  the  blends  chiefly  used  were  composed  of  equal 
parts  by  volume  of  cement  and  tufa. 

In  corroboration  of  his  own  experiments,  the  writer  wishes  to  refer  in 
this  place  to  experiments  made  by  Dr.  W.  Michaelis,  of  Chicago  (the 
younger  Michaelis),  on  blends  made  with  cement  and  puzzolanie  material 
obtained  on  the  Columbia  River.  After  describing  his  experiments,  Dr. 
Michaelis  says: 

“The  experiments  described  in  the  foregoing  show  that  the  puzzolana 
used  in  these  tests  results  in  a commercial  product)  of  excellent  qualities, 
if  reground  with  Portland  cement  in  the  proportions  of  2 parts  of  Port- 
land cement  to  1 part  of  puzzuolana,  or  even  of  equal  parts  of  both  in- 
gredients. The  latter  mixture  has  been  found  to  be  equal  or  even  supe- 
rior to  pure  Portland  cement,  both  in  tension  and  compression,  in  all 
lean  mixtures,  which  correspond  with  actual  working  conditions.  Richer 
mixtures  are  only  rarely  used,  and  should  they  be  desired,  the  puzzuo- 
lana-Portland  cement  mixture  will  prove  to  be  of  especial  advantage  on 
account  of  the  greater  saving  involved.  In  rich  mixtures,  the  pur§  Port- 
land cement  has  been  found  to  be  slightly  superior  in  strength  during 
the  first  months,  but  at  the  end  of  a year  and  at  all  subsequent  dates, 
the  puzzuolana-Portland  cement  mixtures  mentioned  are  equal  to  pure 
Portland  cement  also  in  these  rich  mixtures.  ’ ’ 

Up  to  the  present  time,  the  greater  number  of  experiments  conducted 
by  the  writer  have  been  with  the  “Eugene  puzzolan,”  because  of  its 
known  wide  distribution.  However,  other  materials,  available  in  special 
localities,  are  under  investigation,  and  some  of  them  give  promise  of 
very  excellent  results. 

As  to  the  expense  of  grinding  these  blends,  the  itemized  costs  of  the 
three  mills  used  on  the  Los  Angeles  aqueduct  are  available.  In  compar- 
ing these  costs  with  the  corresponding  items  in  Oregon,  the  writer  sees 
no  reason  why  any  of  the  items  should  be  greater  in  Oregon  than  in 
California,  with  the  possible  exception  of  the  cost  of  power..  The  items 
are:  Cost  of  power,  cost  of  quarrying,  cost  of  mill  operations,  and  gen- 
eral expense,  including  labor,  live  stock,  etc.  The  total  of  these  items  is 
37  cents  per  barrel,  of  which  the  power  item  is  10.5  cents,  and  the  other 
items  26.5  cents.  In  Eugene,  the  California  power  cost  can  be  dupli- 


[9] 


cated,  or  practically  so,  and  doubtless  the  same  can  be  done  in  many 
other  localities,  but  not  in  all.  Probably  a fair  average  cost  in  Oregon 
would  be  40  cents  per  barrel.  The  California  costs  were  obtained  on 
relatively  small  mills,  turning  out  an  average  of  about  16  barrels  per 
hour,  or  enough  in  10  hours  to  lay  about  one-eighth  mile  of  concrete 
road  according  to  the  California  specifications. 

In  any  locality  where  material  equal  to  the  “Eugene  puzzolan”  is 
available,  the  cost  of  a suitable  blend  per  barrel  would  be  figured  by 
taking  53  per  cent  of  the  cost  of  a barrel  of  cement  and  adding  to  thaft 
the  cost  of  blending,  say  38  to  40  cents.  For  example,  the  cost  of  cement 
in  Eugene  in  carload  lots  is  $2.38  per  barrel,  net.  Allowing  for  a 3-mile 
haul  from  the  railroad  to  the  location  of  the  plant,  at  20  cents  per  ton- 
mile,  the  cost  of  hauling  per  barrel  would  be  10  cents,  making  a total  of 
$2.48  per  barrel  for  the  cement.  The  cost  of  the  blend  would  then  be  as 


follows : 

Cement,  .53  barrel,  at  $2.48 $1,315 

Total  cost  of  blending,  say 38 


Cost  of  blend  per  barrel $1,695 


At  Portland  the  cost  of  such  a blend  should  not  exceed  $1.44  per 
barrel,  on  the  basis  that  the  cost  of  cement  at  the  grinding  plant  is  $2.00 
per  barrel. 

It  is  proper  to  remark  that  the  cost  of  the  necessary  grinding  machin- 
ery is  considerable,  so  that  in  order  to  keep  the  cost  of  grinding  low  it  is 
necessary  that  the  first  cost  of  machinery  be  distributed  over  a large 
total  output,  extending  over  several  years,  or  preferably  over  the  eco- 
nomic life  of  the  machinery.  This  w7ould  be  possible,  for  instance,  in 
case  any  county  should  enter  upon  a systematic  plan  of  building  concrete 
highways  for  a series  of  years. 

It  should  also  be  stated  that  the  economy  of  blends  results  from  two 
sources : Nearly  half  of  the  cost  of  cement  at  the  factory  is  saved,  and 
nearly  half  of  the  freight  bill  is  saved.  The  latter  circumstance  explains 
why  it  would  not  in  general  be  economical  to  have  the  blends  ground  at 
the  cement  factory — a suggestion  sometimes  advanced. 

RELATIVE  COST  OF  MACADAM  AND  CONCRETE  ROADS. 

In  considering  the  relative  cost  of  macadam  and  concrete  roads,  it  is 
sufficient  to  consider  those  items  which  are  different  in  the  twTo  cases. 
The  cost  of  grading,  drainage,  shaping  and  rolling  the  roadbed,  and  in 
fact  all  costs  up  to  the  point  of  placing  the  road  material,  should  be  the 
same  *for  macadam  as  for  concrete,  and  these  costs  will  therefore  not 
figure  in  the  comparison. 

Cost  of  Macadam. — The  cost  of  macadam  varies  of  course  within  cer- 
tain limits,  just  as  the  cost  of  anything  else  varies,  depending  on  local 
conditions.  The  very  wide  variations  sometimes  reported  are  generally 
due  to  two  causes : The  very  low  costs  are  for  inferior  construction 
which  would  not  comply  with  standard  specifications;  the  very  high 
eosts  are  generally  due  to  incompetent  management,  though  of  course 
unusual  conditions  sometime  prevail.  However,  the  cost  of  standard 
construction  under  normal  conditions  and  competent  management  is 
fairly  well  known,  and  the  following  typical  cases  may  be  cited: 


[ioj 


In  Massachusetts,  in  1907,  the  average  of  64  contracts  figures  out  54.7 
cents  per  square  yard  of  macadam,  6 inches  thick,  compacted  in  place. 
This  was  for  roads  on  which  local  stone  was  used;  where  imported  trap 
rock  was  used,  the  cost  was  from  10  to  15  cents  greater  per  square  yard. 
In  New  York,  Mr.  H.  A.  Van.Alstyne,  who  was  state  engineer,  at  the 
time  New  York  began  her  recent  good-roads  campaign,  estimated  that  57 
cents  per  square  yard  was  a fair  cost  for  macadam  6 inches  thick  and 
an  average  haul  of  two  miles;  this  with  crushed  stone  at  85  cents  per 
cubic  yard,  common  labor  at  $1.50  per  8-hour  day,  and  team  and  driver 
at  $4  to  $4.50  per  day.  This  figure  (57  cents)  does  not  include  the  con- 
tractor’s profit,  which  was  estimated  at  20  per  cent.  Where  sand  was 
used  as  a binder  in  the  lower  half,  the  cost  was  somewhat  less.  In  New 
Jersey,  in  1908,  the  average  cost  of  146  miles  of  macadam  was  65  cents 
per  square  yard,  including  contractor’s  profit,  which  would  make  54.2 
cents  per  square  yard,  if  profit  be  figured  at  20  per  cent  of  cost.  In 
Lane  County,  Oregon,  last  year,  5 miles  of  excellent  macadam  were  laid 
at  a cost  of  51.3  cents  per  square  yard  for  the  macadam  alone.  This 
figure  does  not  include  interest  and  depreciation  on  machinery.  H.  P. 
Gillette  (“Handbook  of  Cost  Data”)  works  out  an  itemized  cost  of  mac- 
adam in  great  detail  for  an  ideal  case.  If  freight  charges  on  materials 
be  omitted,  then  for  a two-mile  haul,  Mr.  Gillette’s  estimate  would  be 
55.5  cents  per  square  yard  for  6-inch  thickness,  with  crushed  stone  at  75 
cents  per  cubic  yard,  labor  at  $1.50  per  10-hour  day,  and  team  and  driver 
at  $3.50  per  day. 

In  many  cases  the  cost  of  macadam  has  materially  exceeded  the  figures 
quoted  above,  and  there  are  few  if  any  cases  where  the  cost  has  been 
materially  less,  except  where  inferior  construction  was  used,  and  inferior 
construction  is  generally  not  worth  its  cost,  however  small.  On  the 
whole,  it  seems  fairly  evident  that  standard  macadam,  6 inches  thick, 
cannot  be  laid  under  average  conditions  for  much  less  than  54  cents  per 
square  yard.  It  must  be  remembered  that  this  is  for  the  macadam  alone, 
not  including  grading,  drainage,  or  any  of  the  preliminary  operations. 

As  to  the  cost  of  upkeep  of  macadam  roads,  this  varies  widely  of 
course  Avith  different  conditions  as  to  amount  and  character  of  traffic. 
The  intensity  of  traffic  is  constantly  increasing,  and  it  will  be  well  for 
the  people  of  Oregon  to  have  an  eye  to  the  future,  bearing  in  mind  what 
has  already  happened  in  other  places.  A correspondent  of  the  magazine 
“Good  Roads,”  stated  in  the  issue  of  Dec.  7,  1912,  that  macadam  roads 
in  Dallas  County,  Texas,  cost  $600  per  mile  per  annum  for  maintenance. 
This  would  amount  to  6.82  cents  per  square  yard  per  annum  for  a 15- 
foot  road. 

In  speaking  before  the  International  Road  Congress  in  1910,  L. 
Mazerolle,  Engineer  of  Bridges  and  Roads,  Paris,  stated  that  the  cost  of 
maintaining  macadam  roads  reaches  36  cents  per  square  yard  per  year  in 
certain  instances. 

At  the  same  meeting,  Mr.  Austin  B.  Fletcher,  then  Avith  the  Massachu- 
setts HighAvay  Commission,  now  Highway  Engineer  of  Calfornia,  stated 
that  the  maintenance  charge  of  state  highways  in  Massachusetts  has 
increased  from  1.14  cents  to  5.7  cents  per  square  yard  per  annum  in  the 
last  three  years,  that  is  from  1907  to  1910.  During  that  time  Massachu- 
setts’ improved  highways  were  mainly  macadam. 

W.  P.  Judson  (“Roads  and  Pavements”)  states  that  “in  Paris  the 
annual  cost  of  maintenance  of  suburban  macadamized  streets  having 


[ii] 


light  traffic  is  about  one-third  the  original  cost  of  building  them.  In 
some  cases  of  extra  heavy  city  traffic,  the  annual  care  costs  one-third 
more  than  the  original  building.”  That  is  to  say,  under  light  suburban 
traffic,  a macadam  road  has  to  be  rebuilt  every  three  years,  and  under 
heavy  traffic  every  nine  months. 

In  examining  the  reports  of  numerous  State  Highway  Commissions, 
the  writer  has  found  many  instances  where  the  cost  of  maintaining  mac- 
adam roads  is  tabulated  at  $1000  per  mile  per-  annum,  or  more,  and 
$500  or  over  is  a frequent  figure. 

In  an  address  delivered  at  Chicago  last  summer,  Mr.  Logan  W.  Page, 
Director  of  tlie  United  States  Office  of  Public  Roads,  made  the  following 
statement:  L ‘ Figures  collected  by  the  office  of  public  roads  relative  to 
the  cost  of  maintenance  of  plain  macadam  and  bituminous  macadam 
pavements  under  fairly  heavy  traffic  conditions  indicate  that  these  pave- 
ments, when  properly  maintained,  entail  an  annual  absolute  maintenance 
charge  of  approximately  $450  per  mile  per  annum  for  plain  macadam, 
and  possibly  from  $800  to  $1000  per  mile  per  annum  for  bituminous 
macadam,  for  15-foot  surfaces.  These  figures  have  led  me  to  believe  that 
we  must  seek  a more  permanent  form  of  pavements  for  country  road 
surfaces.”  These  figures,  collected  by  the  United  States  office  of  public 
roads  make  the  cost  of  maintenance  per  square  yard  5.11  cents  per  an- 
num for  ordinary  standard  macadam,  and  about  double  this  for  bitumin- 
ous macadam. 

This  is  what  Oregon  is  coming  to  in  the  next  few  years,  in  the  matter 
of  maintaining  macadam  roads,  if  the  state  makes  the  progress  for  which 
all  loyal  citizens  are  hoping.  Maintenance  costs  published  only  a few 
years  ago,  now  appear  ludicrous.  Five  years  ago  the  Massachusetts 
Highway  Commission  thought  they  would  be  able  to  maintain  their  roads 
indefinitely  at  a cost  of  2.25  cents  per  square  yard  per  annum,  but  with- 
in three  years  the  cost  had  soared  to  5.7  cents,  and  now  the  attempt  to 
maintain  macadam  roads  has  been  practically  abandoned,  and  all  sorts 
of  surfaces,  patented  and  otherwise,  are  being  tried  out  in  the  hope  of 
saving  some  of  the  many  millions  of  dollars  which  the  state  has  put  into 
macadam  roads. 

In  New  York,  the  experience  has  been  the  same,  and  so  nearly  every- 
where throughout  this  country  and  Europe.  The  cases  cited  are  merely 
typical  of  what  is  happening  generally,  where  the  people  are  progressive 
enough  to  utilize  the  roads.  But  there  is  no  thought  anywhere  that  the 
right  of  the  people  to  use  the  roads  for  which  they  have  paid  shall  be 
curtailed.  On  the  other  hand,  the  people  are  calling  for  more  and  better 
roads,  and  are  insisting  that  the  roads  must  be  made  to  serve.  The  state 
of  New  York,  in  a popular  election  last  November,  voted  another 
$50,000,000  for  roads,  and  the  measure  earned  in  every  county. 

The  mileage  of  improved  roads  in  Oregon  at  present  is  relatively  in- 
significant and  almost  wholly  disconnected;  so  of  course  the  traffic  is 
small,  since  no  large  traffic  is  possible,  and  the  present  cost  of  main- 
tenance is  low.  But  witih  the  expected  development  of  the  state,  it  is 
safe  to  say  that  the  cost  of  maintenance  of  macadam  roads  within  the 
next  five  or  ten  years  will  have  reached  the  cost  already  passed  in  so 
many  places,  and  the  figures  given  by  the  office  of  public  roads  in  the 
quotation  above  may  be  regarded  as  a conservative  estimate  of  the  cost 
which  we  must  shortly  expect,  namely,  5.11  cents  per  square  yard  per 
annum. 


[12] 


Cost  of  Concrete  Roads. — It  is  the  present  purpose  to  compare  the  cost 
of  concrete  roads  with  the  cost  of  macadam  roads  subject  to  the  traffic 
conditions  just  considered.  In  making  such  a comparison  the  first  ques- 
tion that  arises  is  this : What  thickness  of  concrete  may  be  fairly  com- 
pared with  the  standard  thickness  of  6 inches  for  macadam?  Plainly, 
it  is  not  fair  to  compare  6 inches  of  concrete  with  6 inches  of  macadam, 
because  concrete  is  far  stronger  than  macadam,  and  any  comparison  that 
pretends  to  be  fair  and  rational  must  take  this  fact  into  account.  No 
sane  person  would  think  of  comparing  the  cost  of  a steel  bridge,  for  in- 
stance, with  the  cost  of  a wooden  bridge  on  the  supposition  that  the  vol- 
ume of  steel  should  equal  the  volume  of  wood;  on  the  contrary,  the 
relative  volumes  would  be  made  to  correspond  with  the  relative  strengths 
of  the  two  materials,  and  the  same  consideration  should  govern  the  com- 
parison of  concrete  and  macadam.  While  it  is  not  possible  to  state  with 
precision  just  what  thickness  of  concrete  is  equivalent  to  6 inches  of 
macadam,  it  is  possible  to  state  that  4 inches  of  good  concrete  will  have 
greater  supporting  power  than  6 inches  of  good  macadam  on  the  same 
subgrade,  and  conversely  in  any  location  where  4 inches  of  concrete 
would  not  be  sufficient,  neither  would  6 inches  of  macadam  be  sufficient. 
Where  a weak  subgrade  requires  6 inches  of  concrete,  at  least  9 or  10 
inches  of  macadam  would  be  required  to  give  anything  like  the  same 
supporting  power;  and  where  on  a good  subgrade  6 inches  of  concrete  is 
required  on  account  of  very  heavy  individual  loads,  macadam  should  not 
even  be  considered.  A thickness  of  4 inches  is  considered  the  minimum 
permissible  for  a concrete  base,  and  if  we  compare  this  thickness  with  6 
inches  of  macadam,  the  comparison  will  be  more  than  fair  to  macadam; 
but  to  compare  the  cost  of  concrete  and  macadam  inch  for  inch,  as  has 
sometimes  been  done,  is  an  absurdity  of  which  no  engineer  should  be 
guilty. 

In  cities  the  thickness  of  concrete  base  for  pavements  varies  from  4 
to  6 inches,  the  latter  thickness  being  generally  used  for  heavy  traffic. 
For  the  large  mileage  of  concrete  roads  now  under  way  in  California,  a 
4-inch  thickness  has  been  adopted,  and  the  California  Highway  En- 
gineer is  not  a novice  at  the  business.  There  are  other  competent  men 
who  believe  that  a thickness  of  4 inches  of  concrete  is  sufficient.  Mr. 
George  C.  Warren,  president  of  Warren  Brothers  Company,  in  a paper 
read  before  the  sixteenth  annual  convention  of  the  American  Society  of 
Municipal  Improvements,  stated  that  in  his  judgment,  based  on  over 
twenty-five  years  of  experience,  under  ordinary  conditions  of  well-rolled 
sub-soil,  4 inches  of  concrete  was  ample,  provided  the  concrete  was  not 
disturbed  until  thoroughly  set.  He  stated  further  that  he  had  many 
cases  of  practical  experience  to  back  his  judgment,  and  that  with  a 6- 
inch  base,  one-third  of  the  concrete  was  a wanton  waste,  except  over 
poorly-filled  trenches,  where  settlement  may  occur. 

Even  with  the  prospect  of  a greatly  increased  traffic,  it  hardly  seems 
necessary  that  our  country  roads  should  be  as  heavy  as  the  pavements 
in  the  congested  districts  of  New  York  City,  and  it  appears  probable 
that  4 inches  of  good  concrete  will  be  sufficient,  always  with  the  proviso 
of  proper  drainage  and  compacting  the  subgrade,  for  either  macadam 
or  concrete.  In  special  cases  of  extraordinary  traffic  or  poor  subsoil,  a 
greater  thickness  will  doubtless  be  necessary. 

Assuming,  for  the  purpose  of  comparison,  a thickness  of  4 inches,  we 
may  arrive  at  a fair  estimate  of  relative  cost.  The  writer  favors  a 


[13] 


( 


concrete  base,  with  a thin  bituminous  wearing-  surface,  as  adopted  in 
New  York  and  California,  but  will  also  give  an  estimate  for  a two- 
course  type  of  all-concrete  road. 

For  the  California  type  the  estimate  can  best  be  arrived  at  by  con- 
sidering the  contract  prices  in  California,  and  making  the  necessary 
changes  to  suit  local  conditions.  The  average  of  six  contracts  in  Califor- 
nia, for  which  itemized  bids  are  at  hand,  covering  56  miles  of  road, 
makes  the  cost  of  concrete  in  place  $3.45  per  cubic  yard,  exclusive  of 
cost  of  cement,  inclusive  of  cost  of  stone  and  sand,  freight  charges  and 
hauling,  mixing  and  placing,  and  protection  from  the.  sun  and  sprinkling 
while  hardening,  and  hauling  the  cement,  which  was  furnished  by  the 
state.  The  concrete  mixture  is  in  the  proportion  1 :2y2 :5.  This  will 
require  about  1.3  barrels  of  cement  per  cubic  yard  of  concrete  rammed 
in  place. 

Taking  conditions  at  Eugene  as  typical  of  local  conditions,  the  cost 
of  a suitable  cement  blend,  equal  to  the  cement  of  which  it  is  made,  as 
previously  stated,  will  be  $1.70  per  barrel,  making  $2.21  for  the  cement 
in  a cubic  yard  of  concrete.  There  is  no  good  reason  why  the  cost  of 
the  remaining  items  enumerated  above  should  exceed  the  California 
price  quoted,  and  in  fact  with  proper  equipment  the  Eugene  price  would 
be  less.  Adding  the  items,  we  obtain  $5.66  as  the  total  cost  per  cubic 
yard  of  rammed  concrete.  Since  one  cubic  yard  will  lay  9 square  yards 
4 inches  thick,  the  cost  of  concrete  per  square  yard,  is  about  63  cents. 

The  cost  of  the  bituminous  surface  or  wearing  coat  in  California  is 
about  5 cents  per  square  yard,  the  bituminous  part  being  a heavy  as- 
phaltic oil  containing  90%  asphalt.  This  price  includes  the  cost  of  oil, 
freight,  hauling,  heating  and  spreading  the  oil,  cost  of  stone  screenings 
and  sand,  hauling  and  spreading  same,  and  in  fact  the  total  cost  of  the 
surface  coat.  The  only  items  which  should  be  increased  for  Eugene 
conditions  are  the  freight  charges  on  the  asphaltic  oil  from  California 
to  Eugene,  and  a possible  increase  in  the  cost  of  fuel  used  to  heat  the 
oil  before  placing.  The  freight  charge  in  carload  lots  is  $1.44  per  barrel, 
and  since  one  barrel  will  lay  about  125  square  yards,  the  extra  freight 
charge  will  add  1.15  cents  per  square  yard,  and  making  a liberal  allow- 
ance of  0.35  cent  for  the  possible  extra  cost  of  fuel,  the  total  cost  in 
Eugene  would  be  6.5  cents  per  square  yard.  This  added  to  the  cost  of 
concrete  figured  above  makes  the  total  cost  of  concrete  and  bituminous 
surface  69.5  cents. 

The  length  of  life  of  this  bituminous  surface  cannot  be  definitely 
stated,  but  experience  with  similar  surfaces  in  the  east  indicate  a prob- 
able life  of  five  years.  To.  be  on  the  safe  side,  we  may  cut  this  time  in 
two,  and  assume  that  the  life  will  be  only  two  and  one-half  years,  o«r 
four  complete  renewals  required  in  a ten  year  period,  or  2.6  cents  per 
square  yard  per  year,  as  an  average  cost  of  maintenance. 

On  the  basis  of  the  preceding  discussion,  the  relative  cost  of  macad- 
am and  of  a concrete  road  of  the  California  type  for  a ten  year  period, 
will  be  as  follows: 

Macadam  Concrete 

First  cost  $0,540  $0,695 

Upkeep  for  10  year  period 0.511  0.260 


Total  per  square  yard 


$1,051  $0,955 


[14] 


This  indicates  a saving  of  9.6  cents  per  square  yard  in  favor  of  the 
California  type  of  concrete  road  over  macadam,  or  about  $845  per  mile, 
for  15-foot  road.  This  saving  is  effected  by  the  use  of  a suitable  cement 
blend.  If  cement  were  used  without  blending,  the  saving  would  be 
wiped  out,  but  the  concrete  road  would  still  compete  with  macadam  on 
the  basis  of  equality  of  costs  for  a ten-year  period,  greater  supporting 
power,  and  a better  road  surface  all  the  time. 

While  it  can  hardly  be  denied  that  a comparison  of  costs  of  4 inches 
of  concrete  and  6 inches  of  macadam  is  at  least  fair  to  macadam,  con- 
sidering the  relative  supporting  power  of  the  two  materials,  yet  the 
question  ought  to  be  raised  whether  or  not  4 inches  of  concrete  is  a 
practicable  thickness  for  Oregon  conditions  generally,  outside  the  larger 
cities.  If  if  is,  then  Mr.  Warren  is  right  in  saying  that  any  greater 
thickness  would  be  a wanton  waste.  Believing  that  a practical  test  is 
of  more  value  than  any  amount  of  opinion  or  argumentation,  the  writer 
intends,  if  possible,  to  construct  a short  stretch  of  concrete  road  during 
the  coming  spring,  substantially  as  described  above,  with  a 4-inch  base, 
and  bituminous  surface.  The  effort  will  be  made  to  find  a location  that 
is  at  once  typical  of  general  conditions,  and  at  the  same  time  subject 
to  fairly  heavy  traffic. 

Without  aiming  to  forestall  the  conclusions  obtained  from  such  a 
test,  the  following  considerations  may  be  adduced  as  pertinent  to  the 
question,  and  as  a sufficient  justification  for  making  the  test.  In  many 
eastern  cities  there  is  a large  amount  of  concrete  base  4 inches  thick, 
laid  years  ago  for  sheet  asphalt  pavements,  on  streets  where  the  traffic 
was  then  light;  in  later  years,  the  traffic,  has  become  heavier,  and  yet 
the  concrete  supports  it  safely,  steam  road  rollers  weighing  12  and  15 
tons  traversing  the  streets  with  impunity.  In  many  cities,  where  a 6- 
inch  base  was  considered  to  be  required  by  the  traffic,  or  other  condi- 
tions, the  concrete  was  made  with  natural  cement,  and  a 6-inch  thick- 
ness of  such  concrete  is  hardly  equivalent  to  4 inches  of  Portland  ce- 
ment concrete.  In  the  city  of  Eugene,  among  the  many  kinds  of  pave- 
ments in  use,  are  some  with  a 4-inch  base  and  a thin  covering  of  bitu- 
men ; they  bear  all  kinds  of  traffic  with  no  evidence  of  injury  to  the  base. 

Another  type  of  road  that'  is  worthy  of  consideration  has  a concrete 
base  and  also  a concrete  wearing  surface  composed  of  a richer  mixture 
than  the  base.  For  the  base  course  the  mixture  described  for  the  pre- 
ceding type  would  be  suitable,  but  for  the  wearing  course  the  writer 
does  not  as  yet  recommend  the  use  of  cement  blends.  Their  resistance 
to  abrasion  has  not  as  yet  been  determined,  and  until  he  can  do  this, 
the  writer  recommends  the  use  of  Portland  cement  without  blending 
for  the  wearing  surface,  iy2  inches  thick.  The  proportions  would  be 
1:2:3 y2,  which  is  the  mixture  adopted  for  one-course  concrete  roads  in 
Illinois.  The  writer  considers  that  the  use  of  sand  mortar  for  a wearing 
course  is  objectionable.  For  this  mixture  about  one  and  two-thirds 
barrels  of  cement  per  cubic  yard  of  concrete  would  be  required.  Taking 
the  cost  of  cement  at  Eugene  at  $2.38  per  barrel  net,  the  total  cost  of 
the  wearing  surface  would  be  $7.58  per  cubic  yard,  or  31.6  cents  per 
square  yard.  This,  added  to  the  63  cents  per  square  yard  previously 
estimated  for  the  4-inch  base,  makes  the  total  cost  of  concrete  94.6 
cents  per  square  yard.  The  wearing  surface  must  of  course  be  laid  im- 
mediately upon  the  base  course,  so  that  the  two  courses  solidify  to- 
gether and  form  virtually  one  course.  The  cost  of  maintenance  for  a 
concrete  wearing  surface  is  not  known,  but  is  undoubtedly  very  low  if 

[15] 


/ 


the  work  is  well  done.  If  the  cost  should  prove  to  be  not  more  than 
one  cent  per  square  yard  per  year,  on  the  average,  this  road  could  com- 
pete in  cost  with  a 6-inch  macadam  road  in  a period  of  ten  years,  under 
the  traffic  conditions  assumed;  but  any  such  comparison  of  costs  would 
be  wholly  unfair  to  concrete,  as  above  stated,  since  the  5y2  inches  of 
concrete  would  be  equivalent  to  at  least  8 or  9 inches  of  macadam  in 
supporting  power,  assuming  both  on  an  equally  satisfactory  subgrade. 
On  a considerable  mileage  of  concrete  roads  built  in  New  York  last 
summer,  the  thickness  was  only  5 inches. 

In  case  roads  are  built  from  the  proceeds  of  bonds,  the  interest  on 
bonds  of  course  is  an  item  in  the  total  cost.  But  since  the  chief  justi- 
fication of  bonds  is  that  they  enable  a large  mileage  of  roads  to  be  built 
and  put  into  service  in  a short  .time,  the  interest  account  may  fairly 
be  balanced  against  the  greater  convenience  and  quicker  use  of  the 
roads.  If  this  does  not  offset  the  interest  charge,  then  bonds  would 
hardly  be  justified.  For  this  reason  no  allowance  for  interest  has  been 
made  in  the  preceding  estimates. 

SUMMARY  AND  CONCLUSION. 

It  is  impossible  to  foretell  how  great  the  .traffic  on  Oregon  roads  may 
become  during  the  next  decade.  But  the  experience  of  other  states  and 
our  own  ambitions  toward  rapid  development  all  point  to  the  conclusion 
that  the  further  construction  of  macadam  roads  will  be  uneconomical 
and  therefore  unwise,  at  least  on  our  more  important  highways.  Concrete 
roads  offer  a far  better  solution,  and  by  the  use  of  methods  which  have 
found  favor  both  in  Europe  and  America,  their  first  cost  can  be 
brought  within  reason,  and  their  ultimate  cost  will  be  less  than  that 
of  macadam. 

The  numerous  experiments  that  have  been  tried  with  bituminous  ma- 
cadam have  in  the  main  proved  costly,  and  the  maintenance  charge  is 
found  .to  be  so  great  that  the  Highway  Commission  of  New  York  has 
declared  that  the  results  do  not  justify  the  cost,  and  the  Commission  has 
therefore  adopted  the  concrete  road  as  a standard  for  future  construct- 
ion. Standard  types  of  city  pavements,  such  as  bitulithic  or  vitrified 
brick,  are  too  expensive  for  the  great  majority  of  country  roads,  and 
concrete  is ‘the  most  promising  material  in  sight  that  embodies  at  once 
a moderate  first  cost  and  reasonable  maintenance  charge.  Macadam 
roads  already  built  may  be  saved,  at  least  for  a time,  by  the  use  of 
various  surface  dressings,  but  such  expedients  do  not  embody  a satis- 
factory policy  for  future  construction. 

In  view  of  the  already  rapid  destruction  of  many  well-built  macadam 
roads  in  Oregon,  and  in  view  of  the  universal  conclusion  that  macadam 
is  not  adapted  to  modern  traffic,  such  as  motor  trucks,  road  tractors, 
and  mechanical  haulage  generally,  and  in  view  of  the  fact  that  such 
traffic  will  in  all  probability  be  the  prevailing  traffic  within  a few  years, 
the  writer  believes  that  any  large  expenditure  in  the  future  construction 
of  macadam,  whether  by  the  state  or  by  counties  individually,  would 
be  unwise  and  result  only  in  bitter  disappointment. 

Hindsight  is  proverbially  better  than  foresight,  but  it  is  vastly  more 
expensive.  If  we  are  to  vote  millions  of  dollars  in  bonds  to  build  good 
roads,  we  may  well  profit  by  experience  elsewhere,  and  seek  a type  of 
construction  that  will  stand  modern  traffic.  “Seize  time  by  the  fore- 
lock;” quit,  grabbing  at  the  fetlock. 

[16] 


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